The overall objective of the research project, supported by this grant since 1961 is to identify the enzymes which utilize complex lipids and elucidate their mechanisms of action, in normal tissues and in the lipidoses. Theoretical and methodological aspects of interaction of enzymes with lipid substrates will be further investigated. For this purpose "soluble" lipids, such as lysolecithin and gangliosides or "insoluble" lipids such as the sphingolipid, sphingomyelin or the neutral glycerides will be interacted with the respective hydrolases. Special attention will be directed to developing assays of sphingolipid hydrolases. The purpose of this is to introduce reliable assays for the diagnosis of lipid storage diseases using the natural lipids rather than water-soluble synthetic substrates. Work will be done on Niemann-Pick's disease with the purpose of completely purifying and identifying the sphingomyelinases and clarifying the biochemical etiology of types C and D of this disease. The enzymatic architecture of the membrane of brain lysosomes will also be studied.